1. Field of the Invention
The invention relates to a fuel cell system including a fuel cell arrangement and an injector for returning the exhaust gas to the fuel cell arrangement. The injector includes an inlet opening, a following nozzle, a following diffuser with an outlet opening and an intake opening for feed of the anode exhaust gas of the fuel cell arrangement to a chamber which has been formed in the area of the nozzle and the entry area of the diffuser. Furthermore, the invention is directed to a fuel cell system with a fuel cell arrangement, a reformer for reforming a liquid or gaseous fuel into a hydrogen-containing gas and an injector for return of the exhaust gas to the reformer, the injector having an inlet opening, a following nozzle, a following diffuser with an outlet opening and an intake opening for feed of the anode exhaust gas of the fuel cell arrangement to a chamber which has been formed in the area of the nozzle and of the entry area of the diffuser.
2. Description of Related Art
Conventionally, the fuel supplied to the fuel cell is not completely consumed in the fuel cell. That is, an anode gas is formed with the residual fuel gases H2 and CO as well as N2, CO2 and H2O. The anode exhaust gas can be re-burned in a burner and can be released into the atmosphere as an exhaust gas. Another alternative has been recirculation of the anode exhaust gas into the fuel which has been supplied to the fuel cell. For example, in fuel cell systems disclosed in published European Patent EP 0 800 708 and corresponding U.S. Pat. No. 5,441,821, the fuel cell system includes supplying the anode exhaust gas again using injectors to the fuel cell arrangement. The injectors used there are built in the aforementioned manner.
Conventional fuel systems are known which have a reformer by which a hydrogen-containing gas is produced from a liquid or gaseous fuel which is supplied in turn to the fuel cell arrangement as fuel. These fuel cell systems are especially advantageous in mobile use, since the initial fuels for reforming to produce the hydrogen-containing gas can be transported and handled much more easily than the hydrogen, as is used in the system of European Patent EP 0 800 708 and corresponding U.S. Pat. No. 5,441,821. A suitable fuel for a reformer is, for example, gasoline or diesel. In motor vehicles, these systems are advantageous in that the reformer can be operated with the same fuel as the internal combustion engine of the motor vehicle.
The concept of “fuel” which is being used within the framework of this invention comprises not only the energy sources used, but also a fuel mixture composed for example of the energy source and the oxidizer, for example in the form of air, necessary for reforming.
One suitable process for reforming is the so-called partial oxidation method. In this process, the fuel is oxidized with atmospheric oxygen by sub-stoichiometric combustion. The reforming reaction proceeds at high temperatures, in the 1300° C. range. One known problem in partial oxidation is soot formation. The danger of soot formation can be reduced by the addition of water to the fuel which has been supplied, for example, in vapor form, to the reformer. Adding water to the fuel reduces the danger of soot formation. The anode exhaust gas is also suitable for addition for this purpose. That is, water forms on the anode of the fuel cell arrangement, the amount formed being sufficient to reduce soot formation in the reforming process. In order to supply the fuel to the reformer and to mix the fuel with the anode exhaust gas, an injector can be used, as was described above in an application for injection of a fuel into the fuel cell arrangement.
Both when the fuel is being supplied to a fuel cell arrangement and also when a fuel is being supplied to a reformer there is the problem during the starting phase of the system. That is, the supplied fuels are not yet suitable or the reformer and the fuel cell arrangement have not yet reached the necessary operating temperature to enable proper operation. Consequently, the fuel must be prevented from being delivered.
One suitable alternative for the starting phase of the fuel cell system is to divert the fuel before entering the reformer or the fuel cell arrangement and deliver it to a different use. In order to do this, there must be a valve which delivers the fuel either to the reformer or an afterburner. Similarly, there can be such a valve upstream of the fuel cell arrangement.
While this arrangement does solve the problem of the starting phase, this system is comparatively expensive. Additionally, both the valves and the injectors have a complex structure. Moreover, there additional piping is necessary which makes the system structure more complicated and leads to pressure losses and higher costs.